My one big contention is that if you are doing this AS A PAID PROFESSIONAL, you don't tempt destiny. The last thing you want is something that will cut out randomly. Even ONCE per gig is too much. After a couple of drop outs, and the antics that follow, the people signing your cheques will likely let you go and not rehire you. It's simply not worth it to cheap out.
Anything that is under $100US is strictly home use. Anything between $400-$600 is possible, but you need to do EXTENSIVE testing and have a reliable backup for if/when they do drop out. At around the $1000+ dollar amount, you should be safe (but test anyway!!).
I say should because here is another possible kicker... you need to know that it is a very strong possibility that having 2 of the transmitters on your belt in a dual mono setup at a time
could interfere with each other (even a dual Sennheiser $3000 setup) may not likely be the best answer!
Larry (Keybrdman), here has tried 2 good quality transmitters to try out a stereo setup and they basically were so intermittent and interfered with each other that he now plays in MONO from his accordion, but that just works for him and his needs.
All that I said above... before anyone calls me a hypocrite (lol) I am not a musician that gigs professionally much anymore, BUT I did have a paid gig recently and I did use my
Getaria wireless stereo transceivers. I first setup my entire stage of equipment and tested with a WIRED setup for about 1 hour and it was 100% working and perfectly reliable, I then simply went wireless on the accordion with these transmitters so that I could see how they worked. The backup plan was to have the wires within 3 feet of me and all I needed to do was unplug the cables from the accordion and plug in the wires and done... 30 second delay on a bad day.
I tested the wireless system not only walking around the stage and from end to end, but off the stage on to the dance area and checked distances, often spinning around 360 degrees slowly to find drop outs while playing. I found the range limitation (less than I thought it would go... I started to lose connectivity with my back away from the stage, at around 50 feet) and mentally marked the distance to not go past. I never had any intentions of playing amongst the dancers because my wireless MIDI has a much lower limitation of about 30 feet.
It was really cool that I was able to start playing off stage, walked on music blaring and got the party started... instant ovation.
That darned battery issue: I knew that there was no way that the Getaria batteries would last the 4 hours I was supposed to play for (I know because at home they start to get low at about the 2-3 hour mark, and I found an answer to that at Walmart for $12 in those displays before the cashes on the way out. I bought 2 external 4000mah USB rechargeable battery packs and tested them out on the transmitters... they would power the transmitter and receiver units an easy (tested!) 12 hours with power to spare. I connected one to the receiver and one to the transmitter velcro'ed both to my accordion strap. They are small, black, cheap and perfectly resolved that issue and again, previous testing proved to me that I could charge AND use the transceivers at the same time (something one should do before hand, right??).
So, I kinda broke my own advice, because the location let me be in a very interference-free zone, I extensively tested the wireless units on location, and most importantly, had a fast and easy backup plan to go to in case I needed to. I also would not do this on a regular basis, my good name is worth more than the
risk of losing connectivity in the middle of a song.